Noob question about impedance

[Engine Joe]

Hi -

I have an Onkyo 702 receiver and am in the process of getting new loudspeakers. I noticed in the manual for the receiver that it is dangerous to use this particular receiver with speakers with impedance of under 6 ohms.

Some of the speakers I am looking at have two impedance specs - minimum and nominal. When the word impedance is tossed around casually, or on its own, which does it refer to - minimum impedance or nominal impedance?

The long and the short of it is, if a speaker has 4 ohm minimum impendance and 6-8 nominal impedance, would that be safe with my 6-ohms-and-up only receiver?

 

[annunaki]

First off impedance is not constant, except when the drivers are stationary. Minimum impedance refers to the lowest the impedance will dip at a given frequency throughout its range. Nominal impedance refers to the resisance (impedance) of the speaker at rest. Or at least the number (whether 4, 6 or 8) closest to the actual dc resistance at rest.

In your case, if the speaker has a 6 ohm nominal impedance, it should work fine on your receiver. The minimum impedance is typically only going to be reached at a certain frequency (usually pretty low). It will also be very brief. Any well made receiver should not have problems.

When "tossed around casually", as you put it, it refers to nominal.

 

[Engine Joe]

Thanks! Off to market for speakers go I!